The present invention relates to utility knives having replaceable blades, and more particularly to a utility knife which includes a blade retention feature to prevent the blade from releasing from the knife during use.
Utility knives having replaceable blades and with a variety of end uses are well known in the art. Exemplary of such utility knives are U.S. Pat. Nos. 3,107,426, 3,872,591, 3,577,637, 4,242,795, 4,586,256, and 4,663,845. Such knives incorporate a blade carrier which mounts and supports a blade in the interior of the knife handle. Typically, the blade will include one or more notches on an upper edge which seat against one or more laterally extending posts or lugs on the blade carrier to restrain the blade from longitudinal movement. The blade carrier may also incorporate a thumb actuated button that is depressed to unlatch the blade carrier and blade from one of several latched positions and then moved forwardly or rearwardly to extend or retract the blade. The respective knives are adapted so that mounting and replacement of the blades is relatively simple. For example, in many instances, the knife comprises a pair of complementary halves which are held together by a screw or the like. Loosening or removal of the screw permits the knife to be disassembled and the blade accessed.
However, while such knife designs generally operate in an efficient manner, one continuing problem with them has been the tendency of the blades to release or disengage from the blade carrier during heavy use, particularly where strong lateral or twisting forces are imposed on the cutting edge of the blade. The twisting or lateral movement of the blade may cause the nose of the knife to open slightly. This, in turn, may permit the blade to release from the lugs or posts on the blade carrier and the knife handle, resulting in the need to stop using the knife and to reassemble the knife and blade. The release of the blade from the knife during use also potentially poses a safety problem.
Attempts have been made in the art to overcome this problem. One approach is taught in the above-mentioned U.S. Pat. No. 4,586,256, where the blade carrier includes a tab which has an overhanging bearing edge which is spaced from the blade carrier and which captures the blade to retain it against the blade carrier and prevent it from twisting laterally. Another approach is taught in the above-mentioned U.S. Pat. No. 4,663,845, which teaches the use of a retaining tab for the blade on the rear edge of the blade carrier in combination with a protrusion on one of the facing knife halves which together restrain the blade against twisting lateral movement.
However, while the prior art approaches have addressed the problem, the need still exists for a simple solution which permits a knife having the desired blade retention features.